Canadair began studying Vertical/Short Takeoff and Landing (V/STOL) technology in the mid-1950s at the request of the Canadian Defence Research Board, but it was not until February 1963 that a go-ahead was given for production of a prototype, designated the CL-84, and funded jointly by Canadair and the Government.
The CL-84 was a fairly conventional looking, high-wing, twin-engined design, but it could fly in a way that was anything but conventional. It could take off, fly and land like an ordinary airplane but could also take off, climb, descend and land vertically, like a helicopter--and like a helicopter it could hover. What made this possible was its tilt wing. With a flick of a switch, the pilot could tilt the wing and engines to any position from horizontal to past the vertical. With the wing horizontal, the CL-84 operated like an ordinary airplane. With the wing tilted half-way up, it could make short takeoffs and landings and tight turns. With the wing vertical, it flew just like a helicopter.

The design, manufacture and installation of the V/STOL features of the CL-84 were all new to Canadair. The features included engine, oil and fuel systems which functioned equally well whether horizontal or vertical; a mechanism which tilted the wing and engines; complex shafting linking the engines so that, if one engine failed, that engine would disengage and the aircraft would be powered by the remaining engine, and finally a mixing box which produced the same reaction to the pilot's control movements regardless of whether the aircraft was flying vertically or horizontally.

This box, designed by Karl Irbitis, was an ingenious arrangement of cams and levers which enabled pilots to fly the CL-84 without having to learn a whole new technique - the mixing box did the thinking for them. For example, to bank the CL-84, the pilot moved the control column to one side or the other as in a normal airplane. In conventional flight, this operated the ailerons, but in vertical flight it varied the blade angle of the propellers. In either case the result was the same - the airplane banked. Similarly, a turn, normally made by moving the rudder, was produced in vertical flight by deflecting the ailerons. A climb or dive, normally the result of moving the elevator, was achieved by varying the thrust of the tail rotor when hovering or flying vertically.

When the CL-84 rolled out on December 9, 1964, its most noticeable features were its short, square wing with full-span leading flap and trailing edge flap/ailerons; its two engines located at mid span to enable their huge propellers to "wash" the entire span; a variable-incidence tailplane but no elevator, and two horizontally mounted, contra-rotating tail rotors.

Inside the cockpit, the pilot had a conventional stick and rudder but only one throttle lever. Termed a "power lever", it controlled not only the power of both engines but also (in V/STOL flight) propeller blade angle. A switch on the top of the lever controlled wing tilt.

The prototype CL-84 flew for the first time on May 7, 1965, and completed 145.5 hours in 305 flights before it was lost due to the failure of an off-the-shelf bearing. Nevertheless, the Canadian government was sufficiently impressed with the aircraft's performance to order three updated CL-84-1s for evaluation.

CL-84-1

Slightly longer and more powerful than the CL-84, the CL-84-1 could carry 12 passengers, three 450-kg (1,000-lb) stores on under-fuselage hardpoints or two 460-litre (100-imp. gal) jettisonable fuel tanks on outboard hardpoints. The first CL-84-1 flew on February 19, 1970.
Two CL-84-1s were tested extensively by a total of 40 pilots from NASA, the US Navy, the US Marines, the RAF and the CAF. The aircraft demonstrated its ability to operate at sea in two remarkable sessions aboard the US mini-carriers, Guam and Guadalcanal. The witnesses to these demonstrations were amazed at the ease with which the 84 took off, flew around and landed in blustery wind conditions often reaching 40 knots, particularly as the Canadair pilot involved had never set foot on a carrier before.

The CL-84 was favoured to win two U.S. V/STOL competitions; one for the Combat Aircrew Rescue Aircraft, the other for the Sea Control Ship, but neither advanced beyond the study stage. The CL-84 program was terminated in September 1974 for lack of funds after the three aircraft (the third CL-84-1 was never completed) had accumulated 476 hours in 709 flights.

The CL-84 was a technological success but a marketing failure. CL-84 program manager Fred Phillips suggested three reasons: 1) At that time, interest was centred on jet propulsion and the propeller was considered obsolete technology. 2) Largely as a result of the negative attitude toward propellers, nobody in senior military circles felt strongly enough about the tilt-wing to be its champion when it came to putting money into the budget for production, and 3) the 84 was aimed almost exclusively at the US market but the NIH(not-invented-here) factor makes it very difficult to sell in the US, even with a US partner, especially if the product in question is not in use in the seller's own country.

Where are they now? No.4002 CL-84-1 can be seen at the Canada Aviation Museum in Ottawa. No.4003 belongs to the Western Canada Aviation Museum in Winnipeg, Manitoba.

An interesting account of the evolution of V/STOL aircraft can be found at International V/STOL Historical Society

CL-84-1 Specification